In typical combined cycle power generation systems, cooling of gas turbine high temperature components and the accompanying steam cycle are usually of the following types:
(1) Air Cooled Gas Turbine--The gas turbine high temperature components are cooled by air extracted or conducted from other components in the cycle. The steam cycle and the gas turbine coolant streams are not integrated.
(2) Water Cooled Gas Turbine--The gas turbine high temperature components are cooled with water in the liquid phase. The heat extracted from the high temperature gas turbine components is integrated with the combined cycle steam bottoming cycle. The energy extracted from the high temperature section of the gas turbine is transported to the low temperature portion of the steam cycle to maintain the water in the liquid phase, thus compromising thermal efficiency of the cycle.
(3) Steam Cooled Gas Turbine Integrated Into a Combined Cycle with Multiple Pressure--This cycle uses steam from the low pressure section of a multiple pressure combined cycle to cool the high temperature components of the gas turbine with energy extracted from the gas turbine returned to the low pressure section of the steam cycle. This system is described in U.S. Pat. No. 4,424,668. The thermal efficiency that can be achieved by this system is inferior to that achievable with this invention, however, because, in the '668 system, energy is transported from the high temperature part of the cycle to a low temperature section of the cycle for conversion of the heat energy to power.